1. Field of the Invention
This invention is related to land vehicles and, more particularly, an improved method and apparatus for adjusting the camber of the wheels of such vehicles.
2. Description of the Prior Art
The importance of being able to accurately adjust the camber of a wheel of a vehicle is well known. Without precise adjustment of camber, tire wear is increased significantly and operating costs rise because tires must be replaced more frequently than is the case with wheels whose camber is correctly adjusted. If a tire mounted on a wheel having incorrect camber adjustment is not replaced, then it will ultimately wear out and become a safety hazard.
Camber adjustment is particularly critical on the front wheels of a vehicle and the problem is compounded when the vehicle has four-wheel drive. Of course, it is well known to those skilled in the art that in any vehicle the camber adjustment of the front wheels is more critical than that of the rear wheels. This is true whether the vehicle has four-wheel drive or not. Since the front wheels are used for steering, maladjustments in camber cause more rapid tire wear than is caused by the same maladjustment if present in the rear wheels. It is also well known that poor steering characteristics are a result of camber maladjustments of a vehicle's front wheels.
In vehicles other than those having the conventional four-wheel drive arrangement, the front wheels are usually suspended from the vehicle independently of each other, and the camber of each wheel can be adjusted individually. However, conventionally constructed four-wheel drive vehicles have a rigid front axle with a wheel mounted at each end, and the camber of each wheel cannot be individually adjusted in a practical manner by any known prior art method or by using any known prior art apparatus.
There are at least two known prior art ways of dealing with incorrect camber in front-wheel drive vehicles. The first way is to simply accept the fact that the camber of the front wheels of such vehicles cannot be adjusted and to continually rotate the tires in order to gain maximum mileage from all tires. This is clearly not a solution since it merely causes the relatively unworn tire which is placed on the front axle to wear at a greater rate, rather than reducing the rate of wear itself.
A second approach is to attempt to bend the axle housing to change the angle the wheels make with each other. This approach, while changing the camber of the wheels, introduces large stresses on the parts of the axle which are bent. On occasion, axle housings will break under the stress of bending them, clearly an unacceptable result from the standpoint of the cost involved in replacing the broken axle housing. And even if the axle does not break, these stresses can weaken the axle, rendering it more prone to breakage under operating conditions, thus creating a potentially dangerous situation.
It is also extremely impractical for a manufacturer of such vehicles to attempt to control camber as the vehicle is being made, so that this is not a solution to the problem of incorrect camber either. Adjustments of approximately 1/4.degree. or less are necessary in order to optimize camber, and it is apparent that manufacturing tolerances cannot be held close enough, consistent with minimizing the overall cost of the vehicle, in order to enable such a small angle to be controlled.
Thus, the prior art is lacking a practical and economical manner in which the camber of wheels mounted to a rigid axle can be adjusted, either at the point of manufacture of the vehicle or subsequently. This lack is particularly acute because this is the way that the front axle assembly of a four-wheel drive vehicle is conventionally constructed.